From mboxrd@z Thu Jan 1 00:00:00 1970 From: James Bottomley Subject: Re: [PATCH] 2.6.2-rc2 - MPT Fusion driver 3.00.02 update Date: 28 Jan 2004 15:08:18 -0500 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <1075316397.1739.15.camel@mulgrave> References: <0E3FA95632D6D047BA649F95DAB60E5703D19D33@exa-atlanta.se.lsil.com> <1075136727.2290.48.camel@mulgrave> <401625CA.1070404@torque.net> Mime-Version: 1.0 Content-Type: text/plain Content-Transfer-Encoding: 7bit Return-path: Received: from stat1.steeleye.com ([65.114.3.130]:19605 "EHLO hancock.sc.steeleye.com") by vger.kernel.org with ESMTP id S265923AbUA1UIf (ORCPT ); Wed, 28 Jan 2004 15:08:35 -0500 In-Reply-To: <401625CA.1070404@torque.net> List-Id: linux-scsi@vger.kernel.org To: dougg@torque.net Cc: "Moore, Eric Dean" , SCSI Mailing List , hch@infradead.org On Tue, 2004-01-27 at 02:48, Douglas Gilbert wrote: > So the sg (or SG_IO/SCSI_IOCTL_SEND_COMMAND ioctl) user controls > the data direction and they are free to get it wrong:-) Since we do have a mid layer library for this, perhaps we should set it in sg if the user leaves it apparently unset. > ** The Object Storage Device (OSD) commands use bidirectional > data transfers so perhaps we should think about catering for > that. Actually, a much more fundamental problem for OSD is going to be >16 byte CDBs. The mid and block layers today are coded with an internal 16 byte array for the CDB. That's not very scaleable to the hundreds of bytes that OSD needs. As far as bidirectional goes, we should be able to support that today providing there's just a *single* data buffer, which the OSD spec implies is the easiest way to support this (although I suspect most SCSI processor coding won't be expecting to see both a data in and a data out from a single command). As I see it, OSD seems to require a different interface from the current bio layer, so there would be some type of object layer glue between the fs and the mid-layer, with the block layer relegated simply to queueing specials for the mid-layer, but since no-one's actually come forward with an implementation, that's just a guess. James